The use of pressure measurement guidewires has been in existence for at least the last 10 years. These pressure guidewires are most commonly used to measure the pressure distal to a lesion (stenosis), most commonly in the coronary vasculature. By calculating the ratio between the measured pressure distal to the lesion and some point more proximal, most commonly in the ascending aorta or the coronary tree root, the fractional flow reserve (FFR) is obtained. The FFR is now commonly used to assess the significance of lesion stenosis and thereby to inform the physician as to the most appropriate treatment strategy.
Current devices use piezo-electric pressure transducing elements mounted into a guidewire for measuring blood pressure distal to stenosis that intervene in the calculation of the FFR value. Piezo-electric transducers however suffer from lack of stability as a result of moisture induced sensor drift. Optical pressure element as described in U.S. Pat. No. 7,689,071 do not suffer from such adverse effect and they are better suited for FFR measurement such as for pressure guidewire described in U.S. patent application Ser. No. 13/389,319.
Pressure guidewires also must allow easy disconnection and reconnection of the guidewire to a pressure analyzer. Pressure guidewires involve the measurement of distal blood pressure, followed by the insertion of other interventional medical devices such as Percutaneous Transluminal Coronary Angioplasty (PTCA) balloon catheter over the guidewire for stenting in case of significant lesion. It is however desirable to have the ability to reliably re-connect the guidewire to the pressure analyzer for post stenting FFR assessment, or for multi-vessel lesion assessment. Current electrical connectors such as those described in U.S. Pat. Nos. 4,958,642, 4,961,433, 5,178,159, 5,240,437, 5,358,409, 5,348,481, 5,413,508, 6,196,980, 6,428,336, 7,274,956 are suited for electrical connection. Although they have the ability to provide a reliable electrical connection in dry conditions, they are typically quite sensitive to conditions where the surface of the guidewire connector contacts are contaminated with blood residues after the removal of the interventional device such as PTCA balloon catheter.
A selection of prior art documents is described below. They are discussed for illustrative purposes only. These documents do not necessarily represent the closest prior art.
U.S. Pat. No. 5,125,058 provides a method for optically connecting a guidewire mounted device to a relaying cable. The method however relies on the accuracy of the internal diameter of the guidewire, which is difficult to achieve. The guidewire mounted optical fiber interface is recessed within the guidewire, making the fiber surface polishing a difficult task. The optical portion that is devoted to be inserted into the guidewire needs to be of very small diameter, making the connector very sensitive to mechanical damage.
U.S. Pat. No. 5,601,087 relies on the addition to the guidewire shaft of a proximal tubing portion, often called ferrule, with accurate outside diameter for alignment purpose. The addition of such proximal tubing portion adds extra production steps to the device and represents a challenging assembly process considering the presence of optical parts.
U.S. Pat. No. 6,445,939 also relies on the addition of a ferrule attached to the proximal end of the guidewire shaft. It is indeed very difficult and expensive to machine such a tinny precise ferrule, and to attach it to the proximal end of the guidewire shaft.
U.S. Pat. No. 7,736,301 also relies on the addition of a ferrule near the proximal end of the guidewire shaft. The ferrule is, in this case, not attached to the guidewire as it is desired to allow for rotational connection, hence further increasing the requirement on the diameter tolerance of the parts.
Hence, there is a need for an optical guidewire connector having the ability to reliably connect a guidewire mounted optical pressure sensor to an external pressure analyzer or a similar opto-electronic device; that is disposable, and hence that is easy to produce and is low in cost of material; and that is not sensitive to the presence of moisture or blood contamination.